Method and apparatus for cutting filter materials

ABSTRACT

A method of cutting filter materials in the tobacco industry wherein a filter material in the form of filter rods is fed to rotary knife unit, the filter rods are cut into segments by means of rotary knives pressing the filter rods against a guiding jacket characterised in that the rotary knives are cooled in the area behind the guiding jacket.

The object of the invention is a method and an apparatus for cuttingfilter materials.

In the tobacco industry, particularly in the machines for manufacturingmulti-segment filters used in cigarettes, there is a need of feedingmultiple different filter segments from multiple feeding apparatuses.Among known segment feeding apparatuses are devices for feeding sets offilter segments, whereas one set of segments is formed by cutting onefilter rod transported on a drum conveyor using a cutting head providedwith rotary knives.

Systems for cutting filter materials into segments, in particular filterrods into segments used in multi-segment filters, where a number ofindividual segments with different physical properties is used, areknown in the prior art. Rotary knife units, in particular made of steel,are utilised in the prior art.

In the Polish patent application P.394994, for example, the object ofinvention is a detachable cutting head for an apparatus for feedingfilter segments provided with a drum conveyor having flutes for thetransverse movement of filter rods, provided with rotary knives situatedin knife units fastened in the housing of the head.

The object of invention in the Polish patent application P.395519 is ajacket for guiding filter segments to a filter segment feeding apparatusprovided with a drum conveyor having flutes for the transverse movementof filter rods and a cutting head having multiple rotary knives fastenedin the housing of the head, characterised by having a uniform,substantially cylindrical filter rod guiding surface. In addition, ithas multiple slots for rotary knives of the cutting head.

From the GB 1043706 patent, a detachable cutting head provided withseveral rotary knives mounted on knife shafts is known.

In known filter rod cutting systems, no forced cooling systems are usedbecause rotary knives made of steel easily give off heat to the air withambient temperature. In the course of research on increasing the cuttingspeed, however, difficulties with the maintenance of the cutting surfacequality occurred, whereas the quality of the cutting surface is mainlydecreased by melting thereof. Such difficulties occurred in particularin case of the use of rotary knives made of tungsten carbide. Similardifficulties arose in case of the use of axially incompressible filtermaterials with a high hardness and of materials with the meltingtemperature in the range of 60° C. The purpose of the invention is tosolve the problems which occur during filter material cutting with ahigh speed.

The gist of the invention is a method of cutting filter materials in thetobacco industry wherein by means of a drum conveyor provided on itscircumference with flutes the filter material in the form of filter rodsis fed to a rotary knife unit, the filter rods are cut into segments inthe flutes of the drum conveyor in the area under a filter rod guidingjacket by means of rotary knives characterised in that the rotary knivesare cooled in the area behind the guiding jacket.

Furthermore, a method of the invention is characterised in that therotary knives are cooled to the temperature in the range between 5 and25° C., preferably in the range between 15 and 25° C., and mostpreferably in the range between 20 and 25° C.

Furthermore, a method of the invention is characterised in that therotary knives are cooled with compressed air, water, liquid nitrogen.

Furthermore, the rotary knives are cooled with a cooling medium in aclosed cycle.

Furthermore, the rotary knives are cooled with a cooling medium in anopen cycle.

Furthermore, the gist of the invention is an apparatus for cuttingfilter materials in the tobacco industry comprising a rotary knife unitprovided with a filter rod guiding jacket for guiding filter rodsconveyed in the flutes of the drum conveyor characterised in that in thearea behind the guiding jacket a cooling unit reducing the temperatureof the rotary knives is situated.

An apparatus of the invention is characterised in that the cooling unitcomprises at least one cooling medium blowing nozzle for each knife.

An apparatus of the invention is characterised in that the cooling unitcomprises two cooling medium blowing nozzles on two sides of a knife.

An apparatus of the invention is characterised in that the coolingmedium nozzles are situated substantially perpendicular to the knifesurface.

An apparatus of the invention is characterised in that the coolingmedium nozzles are situated just at the cutting edges.

An apparatus of the invention is characterised in that the cooling unitoperates in an open system. An apparatus of the invention ischaracterised in that the cooling unit operates in a closed system. Anapparatus of the invention is characterised in that the rotary knifeunit comprises rotary knives of tungsten carbide.

An apparatus of the invention is characterised in that the cooling unitis a unit for cooling with air, water or liquid nitrogen.

The substance of the invention is also an apparatus characterised inthat a temperature sensor is assigned at least to one knife.

An advantage of the method and the apparatus according to the inventionis the simplicity of design which allows performing filter materialcutting at high speeds without worsening the physical characteristics ofthe filter material.

The object of the invention was shown in detail in a preferredembodiment in a drawing in which:

FIG. 1 diagrammatically shows an apparatus for cutting filter materialsaccording to the invention.

FIG. 2 diagrammatically shows a view of a cooling head in an openconfiguration,

FIG. 3 diagrammatically shows a view of a cooling head in a closedconfiguration.

FIG. 1 diagrammatically shows an embodiment of the invention in a front,i.e. operator's, view. The drawing shows a drum conveyor 1 mounted on aplate 2 beneath a hopper 3. The drum conveyor 1 conveys filter rods 6picked up from the hopper 3 in flutes 4 on the circumference 5 into theoperating range of a rotary knife 8 unit 7. The filter rods 6 are placedinto the space between the drum conveyor 1 and a guiding jacket 12 wherethey are cut by means of the rotary knives 8. The rotary knives 8 aresituated with their axes of rotation 9 parallel to the axis of rotation10 of the drum conveyor 1, whereas their cutting edges 11 go through theguiding jacket 12 in order to allow cutting of the rods 6 in the flutes4. The rotary knives 8 are partly disposed in a cooling area 15 markedwith a broken line and situated behind the guiding jacket 12. In thecooling area 15, cooling members 16 of a cooling head 17 preferably madeof aluminium are situated, whereas to each knife at least one coolingmember 16 is assigned. The cooling members 16 are members supplying acooling medium to the cooling area 15. The cooling members 16 can be forexample compressed air or gas nozzles; they can also supply a differentcooling medium. The cooling of the cooling head 17 using ice-cold water,i.e. water with additives lowering its freezing point below 0° C., canalso be designed. Also temperature sensors 18 are placed in the coolinghead, whereas at least one temperature sensor 18 at one of the rotaryknives 8 is designed in the cooling head. FIG. 2 shows a diagrammaticview of the rotary knives 8 and the cooling head 17 from the side of thedrum conveyor 1.

During the operation of the apparatus, the rotary knives 8 cut thefilter rods into segments, and their cutting edges and border heat up toa temperature depending on the kind of filter material being cut. Forthe purpose of stabilizing the temperature of rotary knives 8, coolingmembers 16 situated in fragments 19 of the cutting head 17 comprising oradjacent to a portion of the surface of rotary knives 8 have beendesigned in the cooling area 15. The cooling medium will flow to thecooled knives 8 in slots 13 between the fragments 19 of the cooling head17 and the rotary knives 8. The function of the head 17 is to stabilizethe temperature of the rotary knives during their operation. The coolinghead 17 fulfils the function of a heat exchanger to which throughfeeders 21 the cooling medium from a cooling medium source 20 also usedas a system for conditioning, i.e. cooling down and compressing, thecooling medium is supplied. An open cooling system shown in FIG. 2 ispossible where the cooling medium, for example compressed air with a lowtemperature, is released to the environment. A cooling system in aclosed configuration shown in FIG. 3 is also possible where the coolingmedium is supplied through the feeders 21 to the nozzles 16. However,the heated cooling medium is carried from the slots 13 through drains 22to the cooling medium source 20, whereas the medium is not released tothe atmosphere.

In view of the costs, the preferred embodiment of the invention is asystem with a closed cooling medium circulation.

In the preferred embodiments such cooling mediums as compressed air,water, liquid nitrogen are possible.

In the course of the research work, it was unexpectedly observed thatcooling down of the rotary knives of tungsten carbide to the temperatureof 25° C. brought favourable effects for the quality of the filtermaterial cutting process.

During the conducted research it turned out that it was possible tostabilize the temperature of the knives in the range between 5° C. and25° C. Preferably, the temperature was maintained in the range between15° C. and 25° C., and most preferably in the range between 20° C. and25° C.

1. A method of cutting filter materials in the tobacco industry wherein:by means of a drum conveyor provided on its circumference with flutesthe filter material in the form of filter rods is fed to a rotary knifeunit; the filter rods are cut into segments in the flutes of the drumconveyor in an area beneath a filter rod guiding jacket by means ofrotary knives, characterised in that the rotary knives are cooled in thearea behind the guiding jacket.
 2. The method as in claim 1characterised in that the rotary knives are cooled to a temperature inthe range between 5 and 25° C.
 3. The method as in claim 1 characterisedin that the rotary knives are cooled with a cooling medium selected froma group consisting of: compressed air, water, and liquid nitrogen. 4.The method as in claim 1 characterised in that the rotary knives arecooled with a cooling medium in a closed cycle.
 5. The method as inclaim 1 characterised in that the rotary knives are cooled with acooling medium in an open cycle.
 6. An apparatus for cutting filtermaterials in the tobacco industry comprising: a rotary knife unitprovided with a filter rod guiding jacket for guiding filter rodsconveyed in flutes of a drum conveyor, characterised in that the rotaryknife unit comprises rotary knives, and in a space behind the guidingjacket a cooling unit lowering the temperature of the rotary knives bymeans of a cooling medium is situated.
 7. The apparatus as in claim 6characterised in that the cooling unit comprises at least one coolingmedium blowing nozzle for each knife.
 8. The apparatus as in claim 6characterised in that the cooling unit comprises two cooling mediumblowing nozzles on two sides of a knife.
 9. The apparatus as in claim 7characterised in that the cooling medium nozzles are situatedsubstantially perpendicular to the knife surface.
 10. The apparatus asin claim 7 wherein the rotary knives have cutting edges, characterisedin that the cooling medium nozzles are situated just at the cuttingedges.
 11. The apparatus as in claim 6 characterised in that the coolingunit operates in an open system.
 12. The apparatus as in claim 6characterised in that the cooling unit operates in a closed system. 13.The apparatus as in claim 6 characterised in that the cooling unit is aunit for cooling with air, water or liquid nitrogen.
 14. The apparatusas in claim 6 characterised in that a temperature sensor is assigned atleast to one knife.
 15. The apparatus as in claim 6 characterised inthat the rotary knife unit comprises rotary knives of tungsten carbide.16. The method as in claim 2 characterised in that the rotary knives arecooled to a temperature in the range between 15 and 25° C.
 17. Themethod as in claim 16 characterised in that the rotary knives are cooledto a temperature in the range between 20 and 25° C.